# How to Calculate Oligo MW?

beavis beavis at is.nyu.edu
Mon Nov 7 09:05:54 EST 1994

```Peter Myler (mylerpj at u.washington.edu) wrote:
: On 3 Nov 1994 books at mcvax4.d48.lilly.com wrote:

: > We are looking for a formula to calculate the exact MW for oligonucleotides.
: > The oligo will have a 5'-hydroxy group. We can estimate oligonucleotide MW
: > if we use 330 as the average MW for each base but we need a exact number.
: > Thanks DPSMITH smith_dennis_p at lilly.com
: >
: >
: We use MW = (329A + 305C + 345G + 320T) g/mole

: I would appreciate correction if I've got it wrong.

: ===============================================================================
: Peter J. Myler                                 phone: (206) 284-8846x332
: Seattle Biomedical Research Institute          FAX: (206) 284-0313
: 4 Nickerson Street                             e-mail: MYLERPJ at U.WASHINGTON.EDU
: Seattle, WA  98109-1651
: ===============================================================================

The correct formula is

306.179(U) + 304.119(T) + 305.089(C) _345.219(G) + 329.219(A) + 18.015

where U,T,C,G and A are the numbers of the appropriate base and 18.015 is
the mass of water (added only once).  These numbers will give the
correct, isotopically averaged mass for the oligonucleotide.

Ron Beavis
Skirball Institute for Biomolecular Medicine
New York University Medical Center
New York, NY
beavis at is.nyu.edu

```